Generally, when completing a subterranean well for the production of fluids, minerals, or gases from underground reservoirs, several types of tubulars are placed downhole as part of the drilling, exploration, and completions process. These tubulars can include casing, tubing, pipes, liners, and devices conveyed downhole by tubulars of various types. Each well is unique, so combinations of different tubulars may be lowered into a well for a multitude of purposes.
A subsurface or subterranean well transits one or more formations. The formation is a body of rock or strata that contains one or more compositions. The formation is treated as a continuous body. Within the formation hydrocarbon deposits may exist. Typically a wellbore will be drilled from a surface location, placing a hole into a formation of interest. Completion equipment will be put into place, including casing, tubing, and other downhole equipment as needed. Perforating the casing and the formation with a perforating gun is a well-known method in the art for accessing hydrocarbon deposits within a formation from a wellbore.
Explosively perforating the formation using a shaped charge is a widely known method for completing an oil well. A shaped charge is a term of art for a device that when detonated generates a focused explosive output. This is achieved in part by the geometry of the explosive in conjunction with a liner in the explosive material. Generally, a shaped charge includes a metal case that contains an explosive material with a concave shape, which has a thin metal liner on the inner surface. Many materials are used for the liner; some of the more common metals include brass, copper, tungsten, and lead. When the explosive detonates the liner metal is compressed into a super-heated, super pressurized jet that can penetrate metal, concrete, and rock.
A perforating gun has a gun body. The gun body typically is composed of metal and is cylindrical in shape. Within a typical gun tube is a charge holder, which is a tube that is designed to hold the actual shaped charges. The charge holder will contain cutouts called charge holes where the shaped charges will be placed.
A shaped charge is a term of art for a device that when detonated generates a focused explosive output. This is achieved in part by the geometry of the explosive in conjunction with a liner in the explosive material. Many materials are used for the liner; some of the more common metals include brass, copper, tungsten, and lead. When the explosive detonates the liner metal is compressed into a super-heated, super pressurized jet that can penetrate metal, concrete, and rock.
A typical shaped charge is carried in a cylindrical perforating gun. In any type of well, and especially in horizontal wells, the perforating gun will be decentralized. When lying on its side in a horizontal well, the shaped charges on one side of the gun may be further or closer to the casing than on the other side of the perforating gun. Further, it can be difficult to accurately control the direction a shaped charge may fire when located downhole. Most shaped charges create a decreasing hole diameter the further the shaped charge is from the casing. This distance is called the fluid gap in that it is the distance the explosion has to travel through fluid before reaching its intended target. Differently oriented shaped charges on a decentralized perforating gun will each have different fluid gaps with respect to each other.
In many applications it is desirable to have the perforated holes in the casing and formation to be as close as possible in diameter and penetration depth. Discrepancies between the different holes can cause issues later on. For instance, a subsequent fracking operation may not result in equal pressure going into each hole because of the different sizes. A need exists for a shaped charge that will consistently create holes in the formation of similar diameter and penetration depth irrespective of the orientation of the shaped charge.